When a precision machining component subjected to grinding, polishing, or the like, or a component subjected to surface treatment by coating, etc. is tested, surface roughness of the component is an important test item. Conventionally, as for a measuring device that measures surface roughness of a component, for example, a measuring instrument of a sensing pin system has been known for measuring surface roughness by making a tip of a sensing pin contact with a measurement object (see Patent Literature 1).